acetyls alicylic acid (aspirin) synthesis
TRANSCRIPT
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Acetylsalicylic Acid (Aspirin) Synthesis
Telow AJV
Sumicad, CJ, Tavanlar, EMMT, Chem 4!", #nstitute o$ Chemistry, %niversity o$
the &hilippines 'os aos
#! #ntroduction
*r+anic synthesis is the process where a desired or+anic compound is
constructed or prepared $rom commercially availale materials! The o-ective o$
or+anic synthesis is to desi+n the simplest synthetic routes to a molecule!
Aspirin, also .nown as acetylsalicylic acid is assalicylate dru+o$ten used
as anal+esic to relieve minor aches and pains, as an antipyretic to reduce $ever,and as an anti/in0ammatory medication! The history o$ aspirin and its medical
use can e traced way ac. in the second millennium CE! Medicines $rom
willow and other salicylate/rich plants appear in the E+yptian pharmacolo+y
papyri! 1urin+ 4 CE in 2reece, 3ippocrates +ives women willow tree lea$ to
relieve the pain o$ childirth! 3e also used salicylic tea to reduce $evers! illow
ar. e5tract then ecame .nown $or its e6ectiveness in reducin+ $ever, pain and
in0ammation in the mid/ ei+hteenth century! y nineteenth century, pharmacists
were e5perimentin+ with and prescriin+ a variety o$ chemicals related to
salicylic acid, an active component o$ willow e5tract!
#n "789, chemist Charles :r;d;ric 2erhardt treated acetyl chloride with
sodium salicylate to produce acetylsalicylic acid $or the s chemical structure and devised more e6icient methods o$ synthesis!
#n "7?@, scientists at the dru+ and dye
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and remain stron+ in the twenty/
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###!Methodolo+y
A! Schematic 1ia+ram
" +ram salicylic acid in "8/m' Erlenmeyer 0as.
G 9/m' acetic anhydride
G " drop 78H phosphoric acid
/swirl
/ heat in steam ath $or "8 mins
G /m' d3*
G /m' ice cold 3*
/cool to IT
/place in an ice ath
/per$orm suction
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G ?8H ethanol dropwise
swirl until almost all dissolves
G cold d3* dropwise until almost all crystals appear
cool 0as. in a cool ath
suction
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/ warm the tue in water ath $or 8
mins!
/ e5amine mi5ture
Ieaction with :eCl9
pinch o$ the sample in test tue
G 9 drops !8H aDueous :eCl9
G "/m' d3*
/ e5amine mi5ture
1i6erentiation o$ the synthesiFed acetylsalycylic acid $rom commercially
availale aspirin
pinch o$ the sample test tue
G 8 drops 3* and iodine / e5amine
! Set/ups
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"8?LC and a
density o$
"!44+cm9
plenty o$ water
acetic
anhydride
Converts
salicylic acids
hydro5yl +roup
into an acetyl
+roup
a colorless
liDuid with a
density o$ "!7
+cm9
Corrosive and
0ammale
eep away
$rom heat!
ear +loves,
eye protection
and $ace
protection
phosphoric
acid
Serves as the
catalyst
a colorless
viscous liDuid
with a density
o$ "!77 +cm9
and a oilin+
point o$ "87LC
E5tremely
corrosive
Avoid direct
contact! ear
chemical
protective
clothin+
?8H ethanol %sed $or the
recrystalliFatio
n
a colorless
liDuid with a
meltin+ pointo$ ""4LC and a
density o$
@7?!.+m9
S.in and eyes
irritants! 'on+
term use canresult to
serious liver
dama+e
eep away
$rom heat!
ear +loves,eye protection
and $ace
protection
Mn*4 1i6erentiatin+
a+ent
a purple liDuid 3i+hly
e5plosive
when reacted
with
concentrated
sul$uric acid
#n case o$
contact,
immediately
0ush s.in with
plenty o$ water
$or at least "8minutes
:eCl9 :or the
characteriFatio
n o$ the
synthesiFed
aspirin and
commercial
aspirin
rown liDuid
with a molar
mass o$
"B!+mol, a
oilin+ point
o$ 9B LC and
a density o$
!?+m'
Corrosive,
to5ic and
acidic
:lush s.in with
water in case
o$ direct
contact
#V! 1ata
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Tale ""!! 1escription o$ rea+ents
SAM&'E 1ESCI#&T#*K
salicylic acid white, powder/li.e sustance
acetic anhydride clear liDuid with stron+ odor
phosphoric acid clear, colorless liDuid with stron+ odor
?8H ethanol clear, colorless liDuid with stron+ odor
Mn*4 purple liDuid
:eCl9 rown liDuid
#odine solution clear liDuid
Tale ""!9! &reparation o$ Aspirin
SAM&'E 1ESCI#&T#*K
Salicylic acid G acetic anhydride G
78H phosphoric acid
salicylic acid was dissolved
Mi5ture at room temperature crystals were $ormed
Mi5ture a$ter ice ath more crystals were $ormed
Suction :iltrationresidue
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ei+ht o$ watch +lass G
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V! Sample Calculations
"!+ SA ( " mol SA "97!"B +) ( " mol ASA" mol SA) ( "7!"+ " mol ASA) P
"!9+
9! m' AA ( "!7+ AA "m')( " mol AA "!""+)(" mol ASA " mol AA)
("7! "+ " mol ASA) P 8!@+
H yield P Actual yield Theoretical yield Q "H
P !@7+ "!9+ Q "H P BH
H recovery P Iecovery yield Actual yield Q "H
P !48@+ !@7+ Q "H P 8?H
V#! Iesults and 1iscussion
#n this e5ercise, the +oal was to produce acetylsalicylic acid
throu+h the or+anic synthesis $rom the reaction o$ salicylic acid to acetic
anhydride, the startin+ materials! #nstead o$ usin+ acetic acid, acetic anhydride
was used as solvent since the anhydride reactin+ with water to $orm acetic acid
tends to drive the reaction to the ri+ht! #t results $rom the elimination o$ a
molecule o$ water $rom two molecules o$ acetic acid (see :i+! ""!)! :i+ure ""!9
elow shows the alanced chemical reaction o$ the synthesis o$ acetylsalicylic
acid!
:i+ure ""!! Structure o$ Acetic Anhydride
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:i+ure ""!9! The alanced chemical reaction o$ the $ormation o$
aspirin!
ecause the reaction is slow in pure acetic anhydride, the catalyst,
commonly stron+ acids li.e phosphoric acid was used $or the reaction!
Accordin+ to 'e Chateliers principle, the presence o$ e5cess acetic anhydride
$orces the eDuilirium towards the desired product, which in this case is the
aspirin! #n addition to this, the catalysts were also used to ensure that sidereactions, which may cause the percenta+e yield to increase, will e avoided!
The reaction ehind the synthesis is nucleophilic acyl sustitution!
Accordin+ to McMurry (), nucleophilic acyl sustitution happens when the
initially $ormed intermediate e5pels one o$ the sustitutes ori+inally onded to
the caronyl caron leadin+ to the $ormation o$ a new caronyl compound! #n
this e5periment, the speci
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anhydride resultin+ to a tetrahedral intermediate! The hydro5yl +roup (/*3)
attached to the electrophilic caron removed the hydro+en as proton thus
donatin+ the electron to $orm a doule ond (CP*)!The loss o$ the proton
re+enerates the phosphoric acid and thus, producin+ acetylsalicylic acid!
To enhance the synthesis reaction, addition o$ heat and water a$ter
heatin+ were done! The synthesis o$ reaction is $avored y heatin+ the mi5ture
ecause it speeds up the dissolution process o$ salicylic acid and increases its
soluility as well! ecause this speci
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Since the phenol +roup is asent in the synthesiFed aspirin, a ne+ative result
should e otained!
Another test was conducted to di6erentiate the synthesiFed aspirin $rom
the commercially/availale aspirin! :or the iodine test, the positive result is the
solution turnin+ lue or violet ecause o$ the presence o$ starch! #n this
particular e5periment, it is the commercially/availale aspirin that has a colorchan+e which is the solution e5hiited a $aint violet color! Theoretically, this
holds true ecause pharmaceutical companies add starch to talet medicines to
+ive them its characteristic shapes!
'astly, the meltin+ point determination was conducted! *ne way o$
identi$yin+ a sustance is throu+h its meltin+ point! The ran+e o$ the meltin+
point can +ive one an idea on the purity o$ the sample! The theoretical meltin+
point ran+e o$ aspirin is "7/"9@LC! #n this e5periment, the otained meltin+
point ran+e o$ o$ the crude aspirin is "B/ ""LC and $or the recrystalliFed
aspirin, it is ""4/""7LC! The result o$ meltin+ point determination means that
the samples have impurities in it! Karrow di6erence in the meltin+ point ran+eo$ the sample and the theoretical meltin+ point ran+e means that the sustance
is pure ecause o$ the uni$orm $orces present in the molecules! hen the ran+e
is wide, it means that the sample contains impurities! #n this e5ercise, meltin+
point determination is done! And the results show that it has a wide di6erence
$rom the theoretical meltin+ point ran+e o$ aspirin! Thus it can e in$erred $rom
the results that the sample is not pure!
V##! Summary and Conclusion
Synthesis o$ or+anic compounds involves +uidelines and steps that shoulde $ollowed! The
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starch in it! %n$ortunately, :eCl9, did not +ive the theoretical results!
V###! Ie$erences Aspirin timeline! ("9)! Ietrieved on *ctoer 8, "9 $rom
httpwww!tele+raph!co!u.healthhealthnews7"78"B4Aspirin/timeline!html
3istory o$ Aspirin! ("9)! Ietrieved on *ctoer 8, "9 $rom
httpen!wi.ipedia!or+wi.i3istoryo$aspirin
#nstitute o$ Chemistry! (")! asic *r+anic Chemistry 'aoratory
Manual! %niversity o$ the &hilippines 'os aos Colle+e 'a+una! @/@8!
Material sa$ety data sheet! ("9)! Ietrieved on *ctoer B, "9 $romhttpwww!inchem!com!phproductpa+es$ecl9msds!pd$
McMurry, John! ()! *r+anic Chemistry! @thEdition %SA!
MS1S $or potassium perman+anate! ("9)! Ietrieved on *ctoer B, "9
$rom httpwww!sciencela!commsds#dP??@4B
&hosphoric acid! ("9) retrieved on *ctoer B, "9 $rom
httpwww!ccohs!caoshanswerschemicalschempro